Field of the Invention
The present invention relates to the technical field of circuits, and in particular, to a circuit fault detection method and device.
Background Art
Electrical fire accidents caused by power utilization increase year by year and have become the main cause of fire accidents. The existing over-current protection appliances and residual-current protection appliances cannot reduce the electrical fire accident hazards caused by arc faults, and this type of electrical fire accidents accounts for about 30% of all the electrical fire accidents. An arc fault detection device is a novel arc fault protection appliance, and it can detect arc faults in an electrical circuit and open the circuit before an electrical fire accident is caused, thereby effectively preventing electrical fire accidents caused by arc faults in a terminal circuit. An arc fault circuit breaker makes up for the shortcomings of other protection devices, and greatly improves the level of protection against electrical fire accidents.
Some of the existing arc fault detection devices and methods utilize a physical feature such as the intensity of arc light plus an over current amplitude and an over-current change rate which are detected in real time as an identification feature of a fault arc. That method has the following defects:
Firstly, the detection of the over-current amplitude or over-current change rate causes the time of identifying the arc to be late. Meanwhile, the intensity of the arc light of some low-energy arcs is too small to identify. Therefore, these low-energy fault arcs cannot be identified at an early stage. These low-energy fault arcs will develop into high-energy fault arcs, thereby bringing greater impairments. Therefore, it is always desirable to detect the occurrence of a fault arc early so as to trip and extinguish the arc in time when the fault arc is still not sufficient for damaging the circuit breaker apparatus, thereby protecting the workers, the electrical power apparatus and the electrical power system, and prolonging the service life of the electrical power apparatus and the electrical power system. Meanwhile, the level of protection against electrical fire accidents is improved.
Secondly, in a normal electrical line, there exist a large amount of normal arcs, for example, arcs generated from the operation of a switch appliance, arcs generated by an electrical brush of an electric motor, arcs generated by an arc welding machine, arcs generated during the plugging-in of a plug/socket, etc. In addition, many electronic apparatuses will also generate current waveforms and voltage waveforms similar to those of fault arcs. Therefore, the arc fault circuit breaker must be able to distinguish normal arcs from fault arcs accurately; only in this way can protection be provided rapidly and effectively, and the occurrence of erroneous operations can be prevented at the same time, and this is the key technology of the arc fault circuit breaker.
Finally, for an electrical power system having a ZSI (Zone-Selective Interlocking) function, it is more important to detect the occurrence of fault arcs early. In an electrical power system having the ZSI function, circuit breakers correspond to different levels of circuits, and when a failure occurs in a downstream circuit, a circuit breaker corresponding to the downstream circuit trips rapidly and locks an upstream circuit at the same time, so as to realize selective cooperation between levels. However, if the occurrence of fault arcs cannot be detected early, advance current limiting cannot be realized; thus, it is possible that the case where two circuits of different levels are protected at the same time occurs, influencing the implementation of the ZSI function.